1. Field of the Invention
The present invention relates to a control system for controlling a plant, such as an electric power system, a general industrial plant, a public plant and so on, in accordance with state quantities inputted from a plurality of equipment devices of the plant, which include a state quantity input device (input/output device), such as a transformer for instruments and an opening/closing device.
Moreover, the present invention relates to an electric power system protective control system for protectively controlling the electric power system.
Furthermore, the present invention relates to a method of protectively controlling the electric power system.
Still furthermore, the present invention relates to a storage medium storing a program code.
2. Description of the Prior Art
In a plant, such as an electric power system, for controlling state quantities, such as the electric quantities, which are changed as time elapses, a control system having a plurality of digital control apparatuses has widely been operated. The digital control apparatus recognizes a change state of each of a plurality of equipment devices constituting the plant and an abnormal state, such as an accident occurring in any one of the equipment devices, so that stabilizing control and system protective control are performed. In recent years, a high-performance electronic circuit including a high speed microprocessor or a large-capacity memory has been mounted on each digital control apparatus to improve the performance thereof.
As the digital control apparatus for constituting the control system, a variety of apparatuses have been developed to mainly correspond to the contents of the protective control of the electric power system. The control apparatuses are disposed at required locations in the electric power system. Specifically, as an example of the control apparatus, there is a digital relay for detecting an accident (a system accident) occurring in each of equipment devices (power-transmission lines, transformers and the like) of the electric power system so as to separate the accident portion therefrom thereby protecting the electric power system. Moreover, as another example of the control apparatus, there is a fault locator for accurately locating a location of an accident point (a faulty point) on, for example, a power-transmission line. Furthermore, as another example of the control apparatus, there is a system stabilizing relay for performing stabilizing control of the electric power system.
The structure and operation of a digital protective control apparatus (a digital relay) will now be described, which is an example of the digital control apparatus and which performs a protective relay operation for the electric power system.
FIG. 60 is a diagram showing the basic structure of a conventional multi-input digital relay. Referring to FIG. 60, a digital relay 1 is provided with an analog-digital converting unit 2 for taking a multiplicity of analog state quantities (electric quantities), such as electric currents and voltages, from an electric power system to be protectively controlled so as to convert the state quantities into digital state data. Moreover, the digital relay 1 is provided with a digital processing unit 3 for processing protective control operations in response to the digital state data digitized by the analog/digital converting unit 2. The digital relay 1 also has an input/output interface (I/O) 4 for performing an interface process related to a data inputting/outputting operation with respect to the electric power system protective control devices (hereinafter simply called protective control devices, or external devices), such as breakers. The components (the analog-digital converting unit 2, the digital processing unit 3 and the input/output interface 4) of the digital relay 1 are mutually connected to one another through a bus 5 such that data communication is permitted.
The analog-digital converting unit 2 is provided with n analog filters 6-1 to 6-n corresponding to the number of supplied electric quantities (A-1 to A-n) for removing needless frequency components. Moreover, sample hold circuits 7-1 to 7-n corresponding to the analog filters 6-1 to 6-n are provided in the analog-digital converting unit 2 for performing sampling operation. In addition, a multiplexer 8 for selectively outputting and an A/D (analog/digital) converter 9 for performing A/D conversion are provided in the analog-digital converting unit 2.
The digital processing unit 3 is provided with a computer circuit, that is, a CPU (central processing unit) 10 for processing protective control operations; a random access memory (RAM) 11 for temporarily storing electric quantity data and data processed by the CPU 10; a read only memory (ROM) 12 for storing processing procedures (program codes) of the protective control including sequence software constituted by relay software modules; and a nonvolatile memory (EEPROM) 13 for rewritably storing setting values to operate respective relay software modules.
The digital relay 1 is provided with a display device 14, such as an LED, connected to the bus 5 for displaying electric quantity data stored in the RAM 11 by the process of the CPU 10 and the operations of the protective control devices, such as the breakers.
In the thus-structured digital relay 1, n electric quantities A-1 to A-n in parallel taken from the electric power system are passed through the analog filters 6-1 to 6-n so that unnecessary frequency components (a harmonic component except for the fundamental wave, DC component and so on) are removed. Then, the electric quantities are supplied to the sample hold circuits 7-1 to 7-n so as to be sampled in predetermined time intervals (periods) as state values (instantaneous values).
The instantaneous values sampled by the sample hold circuits 7-1 to 7-n are passed through the multiplexer 8 so as to sequentially and selectively be outputted from a single output terminal to the A/D converter 9. The instantaneous values transmitted to the A/D converter 9 are converted thereby into digitized electric quantity data, so that the electric quantity data are sequentially outputted through the bus 5 to the digital processing unit 3.
Electric quantity data sequentially outputting to the digital processing unit 3 are sequentially transmitted to the RAM 11 by a reading process of the CPU 10 in accordance with the protective control program (program code) stored in the ROM 12 so as to temporarily be stored in the RAM 11. On the basis of the electric quantity data stored in the RAM 11, the setting values of the protective relay software modules stored in the EEPROM 13 and contact information of the external devices, such as the breakers, taken through the input/output interface 4, the CPU 10 performs the protective control operation processes (for example, a digital filtering process, an amplitude calculating process, an effective value calculating process, a phase difference calculating process and a process for judging the relay operation of the relay software modules according to the setting value and the like) in accordance with the protective control program stored in the ROM 12.
Results of the protective control operation processes performed by the CPU 10 are outputted by a process of the CPU 10 to the protective control devices (external devices), such as the breakers, through the input/output interface 4 as a protective control operation command, such as a breaking command (a trip command) and a reset command. Thus, the operation for protecting the electric power system {a tripping operation or a reset operation (a contact opening/closing operation) and so on } is performed.
Electric quantity data stored in the RAM 11 are displayed by the display unit 14 by the displaying process of the CPU 10.
Therefore, in the control system having the above-mentioned digital protective control apparatuses, an operator for monitoring the electric power system compares the values displayed on the display units 14 of the respective digital protective control apparatuses with each other. Thus, the operator is able to judge whether or not each of the digital protective control apparatus has a correct state quantity and is normally operated. Incidentally, digital protective control apparatuses except for the digital relay having another protective control function have a structure similar to that of the digital relay 1 in spite of the difference in the contents of the protective control operation processes and the protective control. Thus, a similar operation can be performed.
In recent years, the plants, such as the electric power systems, have been widened and distributed as requirement of the electric power is raised. Therefore, the numbers of the control stations, such as electric stations, for controlling the widely distributed plants and the control apparatuses, such as the digital protective control apparatuses (hereinafter simply called xe2x80x9cprotective control apparatusesxe2x80x9d) provided for the control stations have been enlarged.
To save the monitoring, the operation and the maintenance work of each of the plural control apparatuses, such as the protective control apparatuses, a remote monitoring and controlling system (hereinafter also called a xe2x80x9cremote operational monitoring systemxe2x80x9d) has been invented.
The remote operational monitoring system includes the plural control apparatuses and a display/operation apparatus disposed in a human control station (a human electric station) arranged remote from the control apparatuses. The plural control apparatuses and the display/operation apparatus are connected to each other through a communication network so as to monitor and control the operation of each control apparatus and an operational state thereof from the display/operation apparatus.
In the remote operational monitoring system adapted to, for example, the electric power system, the remote display/operation apparatus transmits, through the communication network, processing demands related to the operation and the operational state of each of the protective control apparatuses. Moreover, the remote display/operation apparatus also transmits a display demand of the state quantity (the electric quantity) supplied from the electric power system. Thus, each of the protective control apparatuses performs processes in response to the demands so as to transmit results of the processes and electric quantity data (digital data converted from electric quantities including electric currents and voltages) to the display/operation apparatus through the communication network. Therefore, the results of the processes and the electric quantity can be displayed on the display/operation apparatus.
As a sophisticated example of the above-mentioned remote operational monitoring system, a system is known, which is disclosed in Japanese Unexamined Patent Publication No. 10-222785 (hereinafter called an xe2x80x9cagent protective control systemxe2x80x9d).
According to the agent protective control system, the display/operation apparatus transmits, to the communication network, a program module including data and procedures for remote monitoring and controlling each of the protective control apparatuses (for example, for setting the setting values of each of the protective control apparatuses, for acquiring and displaying the electric quantity and for performing the protective control operation processes), said data and procedures in the program module being integrated with each other.
The program module moves among the protective control apparatuses through the communication network. Then, each of the protective control apparatuses receives the moving program module so as to perform predetermined control operation processes in accordance with the program module. Next, each of the protective control apparatuses adds an obtained result (a result of the control) and data to the program module so as to transmit the program module to another protective control apparatus.
As described above, the program module moves to, for example, all of the protective control apparatuses through predetermined mobile routes (patterns), after that, the program module moves to the display/operation apparatus. As a result of that, the display/operation unit performs control operation processes including the display process and a fault detection process in accordance with results of the control performed by each protective control apparatus.
Therefore, the agent protective control system is able to eliminate a necessity of individually supplying the process demands and display demands to the multiplicity of the digital protective control apparatuses distributed widely. Thus, it is possible to more efficiently operate and monitor each of the digital protective control apparatus.
On the other hand, FIG. 61 shows a single-line connection employed when the digital protective control apparatuses (digital relays) having the structure and the operation described above are arranged to equipment devices, such as a power-transmission line of the electric power system, a bus line, and so on.
Referring to FIG. 61, power-transmission lines 16A and 16B of an electric power system 15 are provided with power-transmission line protective relays 1A and 1B. The relays 1A and 1B are operative to input state quantities (electric quantities, for example, electric currents and voltages) which flow in the power-transmission lines 16A, 16B and a bus line 17 from a current transformer 18A and a transformer 18B (hereinafter collectively called xe2x80x9celectric quantity transformersxe2x80x9d). In accordance with the inputted state quantities, the relays 1A and 1B performs the above protective control operation processes so as to make the breakers 19A and 19B protectively operate, thereby protecting the power-transmission lines 16A and 16B, respectively.
Similarly, a bus-line protective relay 1C is disposed for making each of the breakers 19A to 19C protectively operate so as to separate the bus line 17 of the electric power system 15 from the power-transmission lines 16A to 16C thereby protecting the bus line 17. Moreover, a transformer protective relay 1D is disposed for inputting, through current transformers 18A,18A, the state quantities which flow upstream and downstream of a transformer 21 of the electric power system 15.
According to the inputted state quantities, the relay 1D performs the above protective control operation processes so as to make the breakers 19C and 19D protectively operate, respectively, thereby protecting the transformer 20.
On the other hand, the digital protective control apparatus, such as the digital relay, constituting the control system is subjected to an operation confirmation test similarly to an analog protective control apparatus, so that the reliability of the digital protective control apparatus is improved, causing the reliability and safety of the electric power system to be improved.
FIG. 62 shows types of operation confirmation tests for the digital protective control apparatus. Among the test items, an acceptance test is taken as an example to described a conventional operation confirmation test.
The acceptance test is performed by sequentially carrying out the tests as shown in FIG. 63. Among the tests, for example, a total operation test is performed such that a test electric quantity is applied to a digital protective control apparatus to be tested so that the test electric quantity is rapidly changed from a steady state to a state similar to an actual accident caused to the electric power system, thereby evaluating the total functions of the tested apparatus. The total operation test is performed by using a system simulating apparatus having a system model produced by modeling configuration elements of the electric power system, such as a power generator or a power-transmission line.
That is, the system simulating apparatus simulates an accident phenomenon (a system fault) previously determined by using the system model so as to produce a test electric quantity data. The tested apparatus is subjected to the test electric quantity so that the operation of the tested apparatus corresponding to the test electric quantity is confirmed. As for a concrete example of the system simulating apparatus, refer to a document (xe2x80x9cPractical Digital Relayxe2x80x9d, p. 152 to p. 154, edited by Izumi Mitani, Ohm).
In each protective control apparatus in the conventional electric power system protective control system, such as the remote operational monitoring system, in a case where the operation confirmation test is performed or actual system accident is performed, when an abnormal state, such as an excess current or an insufficient-level voltage, can be detected by plural relay software modules according to acquired electric quantity data, a trapping command is transmitted to the external device (the breaker) so that the breaker is operated. At this time, each protective control apparatus stores the electric quantity data before and after the operation timing (or trapping operation timing of the breaker) of the plural relay software modules in the RAM for, for example, several cycles.
At this time, by electrically connecting an analyzing tool constituted by a special recording unit and a personal computer to the digital protective control apparatus, a response in the digital protective control apparatus and a change of the state quantity therein are analyzed by the analyzing tool on the basis of the electric quantity data for several cycles before and after the occurrence of the system accident, that is, at which the relay software modules have been operated or the breaker has been operated, whereby a cause of the accident is detected. A result of the analysis of the accident phenomenon performed by the analyzing tool can be processed so that a tester can easily understand the result of the analysis of the accident, thereby displaying the processed result of the analysis of the accident with the monitor.
Therefore, the tester visually confirms data displayed with the analyzing tool so as to confirm the state of response in the digital protective control apparatus related to the system accident. Note that a concrete example of the analyzing tool has been disclosed in the document (xe2x80x9cPractical Digital Relayxe2x80x9d, p. 155 and p. 156, edited by Izumi Mitani, Ohm).
In the conventional digital protective control apparatus, as shown in FIG. 61, since the state quantity of the equipment device of the electric power system to be protectively controlled is received through electric quantity converters 18A and 18B, the digital protective control apparatuses which protect different equipment devices, respectively, that is, the power-transmission line protective relays 1A and 1B, the bus-line protective relay 1C and the transformer protective relay 1D, have different inputted state quantities, respectively.
Therefore, the digital protective control apparatuses for protecting different equipment devices cannot be constituted by the same hardware configuration. Thus, a control system for protectively controlling a multiplicity of types of equipment devices requires digital protective control apparatuses having individual hardware configurations for the multiplicity of the types of the devices, respectively. As a result of that, the cost of the overall system is increased, thereby deteriorating the cost efficiency of the control system.
In the electric stations each of which is provided with the digital protective control apparatus, the equipment devices arranged in protective control regions of the respective electric stations have not the same structure because of limitation of the structure of the equipment device and that of the location of the electric section.
For example, as shown in FIG. 64, a bus line 17A of an electric station 25A and a bus line 17B of an electric station 25B are connected to a power-transmission line 16 through a breaker 19A. A leading portion for leading the power-transmission line of the bus line 17B of the electric station 25B is not provided with a breaker because of the limitation of the location of the electric station 25B.
Therefore, if an accident occurs at an accident point F1 on a power-transmission line 16, digital protective control apparatuses 26A and 26B fundamentally detect the accident in accordance with change of the state quantity flowing in the power-transmission line 16 through the electric quantity converters 18A,18A so as to supply a tripping command to the breaker whereby to quickly separate the accident region from normal regions.
However, in the above-mentioned structure shown in FIG. 64, a breaker is not provided at the leading portion for leading the power-transmission line of the bus line 17B in the electric station 25B. Therefore, the digital protective control apparatus 26A in the electric station 25A transmits a tripping command to the breaker 19A to perform the protective control operation through the breaker 19A.
On the contrary, a digital protective control apparatus 26B in the electric stations 25B forwards (transmits) a breaker tripping command (interruption command) to a digital protective control apparatus 26C in the electric station 25C for protecting a next region.
Therefore, in response to the forwarding interruption command, the digital protective control apparatus 26C outputs a tripping command to the breaker 19B so that the accident region is separated from normal regions.
That is, the digital protective control apparatus 26B must have a circuit (or a process) for outputting the forwarding interruption command to a digital protective control apparatus 26C for protectively controlling the next region. Therefore, the digital protective control apparatus 26A and the digital protective control apparatus 26B cannot be constituted by the same hardware configurations.
The digital protective control apparatus 26C must have a circuit for receiving the forwarding interruption command so as to output the tripping command to the breaker 19B. Therefore, the foregoing apparatus cannot be structured by the same hardware configuration as those of the digital protective control apparatus 26A and that of the digital protective control apparatus 26B.
If the equipment devices for constituting the electric power system in each electric station are different from each other, digital protective control apparatuses having different hardware configurations for the electric stations must be manufactured. As a result of that, the manufacturing cost of the overall control system having the multiplicity of electric stations are raised so that the cost efficiency of the control system deteriorates.
In the control system having a multiplicity of the electric stations having a multiplicity of types of equipment devices to be protectively controlled, since the hardware configurations of the digital protective control apparatuses are different from each other, software (a program) for performing the protective control operation processes, which are installed on the digital protective control apparatuses must be manufactured individually to correspond to the different hardware configurations. Therefore, the manufacturing cost of the digital protective control apparatuses are raised, causing the cost efficiency of the control system to deteriorate. Moreover, tests, operations and management of the software for the protective control operation processes, which is installed on each of the digital protective control apparatuses must be performed individually for each of the protective control apparatuses. Therefore, the cost to perform the tests, operations and the management of the software for the protective control are raised. Thus, the reliability of the software for the protective control deteriorates.
In the conventional electric power system protective control system having a plurality of the digital protective control apparatuses provided for the plural equipment devices, such as the power-transmission lines and bus lines, of the electric power system, and in the electric power system protective control system constituted by connecting the plurality of the digital protective control apparatuses through the communication network to the display/operation apparatus for the remote operational monitoring control, an operator of the remote monitoring operation of the electric power system visually confirms the electric quantity acquired by the digital protective control apparatus through the display unit of each of the digital protective control apparatuses. Therefore, the electric quantities at the same time acquired by the respective digital protective control apparatuses cannot strictly be confirmed, thereby deteriorating the reliability of the electric power system protective control system. Moreover, a multiplicity of electric quantities gained by the plural apparatuses must successively be confirmed by using a multiplicity of display units. Therefore, the burden imposed on the operator performing the visibly monitoring operation increases and the cost efficiency deteriorates due to an increase of the cost of the components of the control system.
With the conventional agent protective control system, in a case where the display/operation unit performs a fault detection process including location of an accident point in accordance with the electric quantity gained by each of the protective control apparatuses, electric quantity data {which are acquired, for example, at angular intervals of 3.75xc2x0 (4.8 KHz) or 15xc2x0 (1.2 KHz)} of the voltage and the electric current, which are results of the control performed by a certain protective control apparatus (a first protective control apparatus), are added to the program module so that the program module with the electric quantity data moves to a next protective control apparatus (a second protective control apparatus). The second protective control apparatus executes the transferred program module so that the electric quantity data gained by the second protective control apparatus are added to the program module. The program module with the electric quantity data moves to a next protective control apparatus (a third protective control apparatus). That is, execution of the program module, addition of the electric quantity data gained by executing the program module, and movement of the program module to a next protective control apparatus are sequentially performed for each of the protective control apparatuses. The display/operation unit performs the fault detection process in accordance with electric quantity data of each protective control apparatus added to the transferred program module.
In order to enable the display/operation unit to execute the fault detection process thereby detecting a fault of the electric power system, electric quantity data detected by the protective control apparatuses at the same timing, that is, electric quantity data precisely (for example, in xcexcs units or a level substantially 1 xcexcs) synchronized with each of the protective control apparatuses must be required.
However, the conventional agent protective control system gains electric quantity data whenever the program module is moved, that is, at different timings among the protective control apparatuses. The communication network, such as a usual telephone circuit, has a possibility that transmission of communication data is delayed by tens of milliseconds to several seconds owning to a state of load on the network or noise. Therefore, it is impossible to transmit synchronizing signals to the protective control apparatuses through the communication network for the purpose of precisely synchronizing the apparatuses each other.
Therefore, in the conventional agent protective control system having the communication network through which the program module is transferred, it is hard to synchronize the electric quantity data acquired by the protective control apparatuses and difficult to accurately detect the fault of the electric power system.
From this viewpoint, in the electric station unit, by laying a signal line to individually from the communication network so as to connect the plural protective control apparatuses in the electric station to each other, it is possible to synchronize the plural protective control apparatuses in the electric station by communicating the synchronizing signals among the plural protective control apparatuses therein.
However, in the above-mentioned remote operational monitoring system, it is very hard, from a viewpoint of cost efficiency and large quantity of operation, to lay the synchronizing signal lines among the protective control apparatuses provided for the plural electric stations distributed widely. What is worse, there is apprehension that the practicality of the remote operational monitoring system excessively deteriorates.
In the conventional electric power system protective control system, such as the remote operational monitoring system, power-transmission line constants (ranging impedances) required in a case of performing, as the fault detection process, the accident determination (detection) process at which an earth fault occurs between, for example, power-transmission lines and a fault locating process for locating the accident point, are set to predetermined values calculated as a mere theory in accordance with design data of the power-transmission lines. Therefore, the electric quantity (the electric current of the power-transmission line encountered the accident) of the actual electric power system cannot be employed. Thus, there is apprehension that the set power-transmission line constants have errors so that there is a possibility that the accurate accident point cannot be located. Furthermore, the power-transmission line constants are fixed to the values which are calculated by using the mere theory. However, since the parameter, such as the electric current in the power-transmission line, for obtaining the power-transmission line constants which always vary because of an influence of variation in the weather conditions, even if the fixed power-transmission line constants are used to locate the accident point, the accuracy in locating the accident point cannot be improved.
In viewpoint of this, in a conventional electric power system protective control system, a measurement device comprised of an operating unit and an memory, which is an individual from the protective control apparatus, has been operated to measure the parameter required to calculate the power-transmission line constants from the electric power system (the power-transmission line). In accordance with the measured value, the power-transmission line constants have been operated by the measurement device.
However, the conventional method of obtaining the power-transmission line constants using the measurement apparatus requires the measurement apparatus provided individually from the protective control apparatus. Therefore, cost efficiency of obtaining the power-transmission line constant deteriorates. To obtain the power-transmission line constants, the measurement apparatus must always be provided for the electric power system (the power-transmission line or the like) to measure parameters required for the power-transmission line constants. Therefore, the power-transmission line constants cannot easily be obtained periodically or as necessary.
The conventional electric power system protective control system, such as the remote operational monitoring system, has the protective control apparatuses each having a single processing unit which performs an input/output process of data which are supplied from the display/operation unit through the communication network, a control demand analyzing process and a process for acquiring the electric quantity. However, a great processing load is required for making the input/output process of data and the control demand analyzing process, and, the process for acquiring the electric quantity from the electric power system at predetermined periods must be performed simultaneously with the input/output process and the control demand analyzing process.
That is, it is very difficult for the single processing unit to simultaneously perform all of the data input/output process through the communication network, the control requirement analyzing process and the electric quantity acquiring process. Therefore, there is apprehension that at least one of the processes is delayed and that the protective control operation for the electric power system protective control system is obstructed.
In the conventional electric power system protective control system, such as the remote operational monitoring system, input/output of data between the digital protective control apparatuses and that between each of the digital protective control apparatuses and the display/operation unit are performed through the communication network.
However, each of electric quantity acquiring devices, such as sensors in the electric power system, and each of the digital protective control apparatuses (its analog input/output interface) are connected to each other through dedicated lines. The equipment devices for operating the breakers (the external devices), such as switches, of the electric power system and each digital protective control apparatus (an I/O interface for outputting the external operation command signals with regard to the external devices) are connected to each other through dedicated lines.
Since large numbers of the electric quantity acquiring devices and the equipment devices for operating the external devices must be provided for the electric power system, the dedicated lines are increased so that the cost for providing the electric power system protective control system cannot be reduced and that a great amount of works for connecting the dedicated lines is required.
In the foregoing electric power system protective control system, the interface is established between the electric power system and the digital protective control apparatuses by the dedicated lines.
In a case where the electric quantity of an equipment device which must be protected by another digital protective control apparatus is sometimes required to be used by a certain digital protective control apparatus among a plurality of the digital protective control apparatuses, the foregoing digital protective control apparatus (a digital protective control apparatus of the root of the requirement) must acquire, through the communication network, the electric quantity fetched through the sensor and the dedicated line from the predetermined equipment device to be protectively controlled by the another digital protective control apparatus.
In this case, the demand-receiving digital protective control apparatus is continuously acquiring the electric quantity from the predetermined equipment device through the sensor and the dedicated line at predetermined periods. That is, the electric quantity (electric quantity data) which has continuously been collected must be communicated to the digital protective control apparatus of the root of the requirement through the communication network. As a result, the communication load must be subjected to a heavy communication load.
When a demand for using the electric quantity is transmitted from the digital protective control apparatus of the root of the requirement, the another digital protective control apparatus must perform a process for successively communicating, to the communication network, the electric quantity (electric quantity data) continuously collected from the electric power system through the sensor. Thus, the processing efficiency of the another digital protective control apparatus deteriorates.
The conventional digital protective control apparatus such as the digital relay, performs the tripping test having the items shown in FIG. 63. The total operation test of the tripping test is a very important test in which a system simulating apparatus is used to simulate the system fault. That is, an obtained test electric quantity produced by the simulation of the system simulating apparatus is applied to the digital protective control apparatus to confirm the total operation thereof.
Among the total operation test to which the conventional digital protective control apparatus is subjected, the system simulating apparatus simulates only the system accident (fault) which has been previously set to the system simulating apparatus. Moreover, the system model cannot accurately model the whole of the electric power system. Therefore, actual and complicated system accidents cannot completely be simulated. For example, electromagnetic induction between the two adjacent and parallel power-transmission lines cannot completely be modeled, which includes a variety of electric fields and magnetic fields acting on the power-transmission lines. Therefore, the foregoing electromagnetic induction cannot be simulated.
In recent years, an actual electric power system has been complicated, and a superimposed power flow (load flow) has been caused from enlargement of the supply and demand of the electric power. Therefore, various and complicated system accidents are expected in the actual electric power system.
However, in the conventional digital protective control apparatus, since the test electric quantity is produced from the simulations of the system accidents by the system model, the total operation test cannot be performed by using a test electric quantity similar to that based on a system accident occurring in an actual electric power system which has been complicated and has the superimposed power flow. Therefore, the reliability of the tested apparatus (the digital protective control apparatus) is reduced.
In the conventional electric power system protective control system, such as the remote operational monitoring system having the plural digital protective control apparatuses, each of the digital protective control apparatuses has the memory. The state quantity (electric quantity data) for several cycles before and after the operation timing are stored in the memory in response to the operations of the plural relay software modules or the operation of the external equipment device, such as the breaker, when the system accident has occurred (or the system accident has been simulated).
In the conventional electric power system protective control system, the protective control apparatus, which has detected an accident, acquires the electric quantity data. However, the other protective control apparatuses around (for example, adjacent) the protective control apparatus detecting the accident do not usually perform the tripping operations of the breakers, though the apparatuses detect the changes in the state quantities caused from the accident (for example, in a case where only a single relay software module has been operated). Therefore, the electric quantity data are not stored in the other protective control apparatuses. As a result, only electric quantity data stored by the protective control apparatus detecting the accident is used to perform the analyzing process for detecting the cause of the accident. Thus, a detailed cause of the accident cannot be analyzed.
As described above, the conventional electric power system protective control system cannot analyze the reaction of the digital protective control apparatus, which is not operated. Therefore, whether or not the operation of the digital protective control apparatus encounters a problem cannot be determined. As a result, if the operation of the digital protective control apparatus is erroneously not operated, the erroneous non-operation of the protective control apparatus cannot be detected. Therefore, there is apprehension that the reliability of the digital protective control apparatus, that is, the reliability of the overall control system deteriorates.
As described above, the conventional electric power system protective control system having the plurality of the digital protective control apparatuses is provided with the memory disposed in each of the digital protective control apparatuses. In response to the timing of the operations of the plural relay software modules or the operations of the breakers when the system accident has occurred, the electric quantity data indicating a state of the reaction in the apparatus and change in the state quantity are stored in the memory. Therefore, when the system accident has occurred, the electric quantity data indicating the reaction in the apparatus and the change in the state quantity are not stored in the digital protective control apparatus having the relay software modules, which are correctly not operated. Total analysis using the electric quantity (the state quantity) of the overall electric power system obtained from all of the digital protective control apparatuses when the system accident has occurred cannot be performed. Therefore, there is apprehension that the reliability of the overall control system deteriorates.
The various problems experienced with the electric power system protective control system for protectively controlling the electric power system apply to control systems for controlling plants in addition to the electric power systems, such as general industrial plants and public plants.
In view of the foregoing problems, a first object of the present invention is to provide a control system and an electric power system protective control system for using digital data (electric quantity data) on the basis of state quantities taken from a plurality of equipment devices constituting a plant, such as an electric power system, so as to control each of the equipment devices, wherein control functions are divided among the equipment devices and processing units for performing the divided functions are connected to each other through a communication network thereby improving the cost efficiency and reliability of the control system and the electric power system protective control system.
In view of the foregoing problems, a second object of the present invention is to provide a control system having a plurality of digital protective control apparatuses for controlling each of equipment devices by using digital data on the basis of state quantities taken from the equipment devices constituting a plant, such as an electric power system, which is capable of subjecting state quantities acquired by the digital protective control apparatuses to comparisons at the same time so as to improve the reliability of the control system and reduce a load which must be applied to an operator for monitoring the plant and part cost of the control system.
In view of the foregoing problems, a third object of the present invention is to provide a remote operational monitoring system, which is capable of precisely synchronizing state quantity data, such as electric quantity data, acquired by a plurality of control apparatuses with each other, without using any signal line for establishing synchronization laid among the control apparatuses (among control stations and among electric stations), thereby performing, for example, an accurate fault detection process.
In view of the foregoing problems, a fourth object of the present invention is to provide an electric power system protective control system which is capable of periodically or occasionally obtaining power-transmission line constants on the basis of an actual electric power system without using a fixed power-transmission line constant and a measurement device which is provided individually from the protective control apparatus.
In consideration of the foregoing problems, a fifth object of the present invention is to provide an electric power system protective control system which is capable of simultaneously and quickly performing a data input/output process through a communication network, a control demand analyzing process and an electric quantity acquiring process.
In consideration of the foregoing problems, a sixth object of the present invention, by establishing interface required to communicate electric quantities and operation command signals between an electric power system and a plurality of the digital protective control apparatus without using a plurality of dedicated lines, is to reduce processing loads of the communication interface for communicating data among the digital protective control apparatuses and among the digital protective control apparatus and a display/operation apparatus, and to reduce an equipment cost of the electric power system protective control system and an amount of operation works required to connect the dedicated lines.
In consideration of the foregoing problems, a seventh object of the present invention is to enable a total operation test to be performed by using the same test state quantity as that caused when a system accident occurs in an equipment device provided for an actual electric power system or the like so as to improve the reliability of each digital protective control apparatus and the reliability of the overall electric power system protective control system.
In consideration of the foregoing problems, an eighth object of the present invention is to provide an electric power system protective control system, in a case where a system accident occurs, when a relay software module or a breaker with regard to a digital protective control apparatus except for the protective control apparatus which is related to the system accident is not operated, said electric power system protective control system performing analysis of a reaction of the non-operated digital protective control apparatus so as to enable a detailed cause of a fault to be detected and a total analysis, thereby improving the reliability of the digital protective control apparatuses and that of the electric power system protective control system.
To achieve such objects, according to one aspect of the present invention, there is provided A control system for controlling a plant according to a state quantity related to the plant and inputted therefrom, said system comprising: a communication network; an input device connected to the communication network so that data communication is permitted, said input device having: means for acquiring precise time, inputting means for inputting the state quantity related to the plant therefrom, converting means for sampling the inputted state quantity according to the acquired precise time so as to convert the state quantity into digital data and first transmitting means for adding the precise time at each sampling timing to the digital data so as to transmit the digital data each having the precise time to the communication network; an opening/closing device connected to the communication network so that data communication is permitted and adapted to opening and closing a part of the plant., said opening/closing device having: means for receiving, through the communication network, a control command with respect to the opening/closing device and second transmitting means for transmitting an operating state of the opening/closing device to the communication network; and a control apparatus connected to the communication network so that data communication is permitted, said control apparatus having: means for performing a control operation process according to the digital data transmitted through the communication network and the operating state of the opening/closing device transmitted therethrough and third transmitting means for transmitting the control command through the communication network to the opening/closing device in response to a result of the control operation process of the performing means.
To achieve such objects, according to another aspect of the present invention, there is provided An electric power system protective control system for controlling an electric power system according to a state quantity related to the electric power system and inputted therefrom, said protective control system comprising: a communication network; an input device connected to the communication network so that data communication is permitted, said input device having: means for acquiring precise time, inputting means for inputting the state quantity related to the electric power system therefrom, converting means for sampling the inputted state quantity according to the acquired precise time so as to convert the state quantity into digital data and first transmitting means for adding the precise time at each sampling timing to the digital data so as to transmit the digital data each having the precise time to the communication network; an opening/closing device connected to the communication network so that data communication is permitted and adapted to opening and closing a part of the electric power system, said opening/closing device having: means for receiving, through the communication network, a control command with respect to the opening/closing device and second transmitting means for transmitting an operating sate of the opening/closing device to the communication network; and a protective control apparatus connected to the communication network so that data communication is permitted, said control apparatus having: means for performing a protective control operation process according to the digital data transmitted through the communication network and the operating state of the opening/closing device transmitted therethrough and third transmitting means for transmitting the control command through the communication network to the opening/closing device in response to a result of the protective control operation process of the performing means.
In preferred embodiment of this another aspect, said acquiring means, said converting means and said first transmitting means are constituted by a computer circuit having hardware elements including a CPU and a memory unit, said computer circuit being provided with means for self-diagnosing an operating state of the computer circuit and means for transmitting a result of the self-diagnosis performed by the self-diagnosing means to the communication network, and wherein said opening/closing device is provided with means for receiving the result of the self-diagnosis transmitted through the communication network and means for locking control of the operation of the opening/closing device in response to the result of the self-diagnosis received by the result receiving means.
This another aspect of the present invention has an arrangement that said input device and said opening/closing device are provided for plurality of electric stations, respectively, said electric stations being distributed, said acquiring means, said converting means and said first transmitting means are provided for the respective input devices of the respective electric stations, said control command receiving means and said second transmitting means are provided for the respective opening/closing devices of the respective electric stations, said control operation performing means and said third transmitting means are provided for at least one of the dispersively disposed electric stations, said communication network is composed of a first communication network in a local area constituted in each of the electric stations and a second communication network for widely connecting the dispersively disposed electric stations to each other, said converting means of each of the input devices in the electric station is adapted to sample the state quantity of its own input device at predetermined periods in accordance with the precise time acquired by the acquiring means while synchronizing the state quantities of the respective input devices with each other, and to convert the sampled state quantities into digital data, said first transmitting means of each of the input devices is adapted to add the precise time at each sampling time to each converted digital data and to transmit the digital data each having the precise time through the first communication network to the second communication network, and wherein said control operation performing means of the at least one of the electric stations has means for receiving the digital data each having the precise time of each of the input devices and the operating state of the opening/closing device transmitted through the first and second communication networks, means for time-sequentially arranging the received digital data in accordance with the precise time of each received digital data for each of the input devices and means for performing the protective control operation process in accordance with the time-sequentially arranged digital data by the arranging means.
In order to achieve such objects, according to further aspect of the present invention, there is provided an electric power system protective control system for performing an operation process in accordance with a state quantity inputted from an electric power system so as to protectively control the electric power system, said protective control system comprising: a communication network; a digital protective control apparatus connected to the communication network so that data communication is permitted, said digital protective control apparatus comprising: means for acquiring precise time, converting means for sampling the state quantity inputted from the electric power system according to the acquired precise time so as to convert the state quantity into digital data and transmitting means for adding the precise time to the converted digital data at each sampling timing so as to transmit the digital data each having the precise time to the communication network; means for receiving the digital data transmitted through the communication network, each of said digital data having the precise time and means for time-sequentially arranging the received digital data each having the precise time in accordance with the precise time of each of the received digital data.
In preferred embodiment, this further aspect further comprises display means for displaying a digital data group time-sequentially arranged by the arranging means.
In preferred embodiment, this further aspect further comprises means for generating a state quantity of a test for a digital protective control apparatus to be tested in accordance with the digital data group time-sequentially arranged by the arranging means.
For achieving such objects, according to further aspect of the present invention, there is provided an electric power system protective control system comprising: a plurality of digital protective control apparatuses for protectively controlling an electric power system; a communication network for connecting the digital protective control apparatuses to each other so that data communication is permitted, each of said digital protective control apparatuses having: means for acquiring precise time, converting means for sampling a state quantity related to a first equipment device of the electric power system at predetermined periods in accordance with the precise time acquired by the acquiring means so as to convert the sampled state quantities into digital data, said first equipment device being an object for protectively control of the corresponding digital protective control apparatus, first judgement means for judging whether or not the first equipment device is faulty based on the converted digital data so as to perform a protective control operation process according to a result of the judgement of the first judgement means, second judgement means for judging whether or not the first equipment device and a second equipment device of the electric power system are faulty based on the converted digital data, said second equipment device being not object for protective control of the corresponding digital protective control apparatus; recording means for, when the judgement of the second judgement means is made that at least one of the first and second equipment devices is fault, adding the precise time to the converted digital data at each sampling timing so as to record the digital data each having the sampled precise time, and means for transmitting the digital data recorded by the record means to the communication network, said transmitted digital data having the sampled precise time; receiving means connected to the communication network for receiving the digital data transmitted through the communication network from each of the digital protective control apparatuses, each of said received digital data having the precise time; and arranging means for time-sequentially arranging the received digital data according to the sampled precise time thereof for each of the digital protective control apparatuses.
In order to achieve such objects, according to still further aspect of the present invention, there is provided an electric power system protective control system comprising: a plurality of digital protective control apparatuses for protectively controlling an electric power system; and a communication network for connecting the digital protective control apparatuses to each other so that data communication is permitted, each of said digital protective control apparatuses having: means for acquiring precise time; converting means for sampling a state quantity related to an equipment device of the electric power system at predetermined periods in accordance with the precise time acquired by the acquiring means so as to convert the sampled state quantities into first digital data, said equipment device being an object for protective control of the corresponding digital protective control apparatus; transmitting means for adding the precise time at each sampling timing to each first converted digital data so as to transmit the first digital data each having the precise time to the communication network; means for receiving second digital data having the precise time transmitted from the transmitting means of at least one of other digital protective control apparatuses through the communication network; arranging means for time-sequentially arranging the received second digital data in accordance with the precise time of each second received digital data; and means for performing a protective control operation process by using one of the first digital data converted by the converting means and the second digital data time-sequentially arranged by the arranging means.
For achieving such objects, according to still further aspect of the present invention, there is provide an electric power system protective control system comprising: a plurality of protective control apparatuses adapted to perform a protective control operation process according to a state quantity related to an electric control system for protectively controlling the electric power system, respectively, said control apparatuses being distributed; and a communication network by which the protective control apparatuses are connected to each other so that data communication is permitted, each of said protective control apparatuses comprising: means for acquiring signals at substantially constant periods; collecting means for sequentially sampling the state quantity related to the electric power system at a same timing as a timing of another protective control apparatus in accordance with the periodic signals acquired by the acquiring means so as to collect digital data; and storage means for adding time at each sampling timing based on the periodic signals to the collected digital data so as to sequentially store the digital data each having the time.
This still further aspect of the present invention has an arrangement that said acquiring means is composed of means for acquiring precise time and the time at each sampling timing is precise time at each sampling timing.
This still further aspect of the present invention has an arrangement that further comprises a monitor/control unit connected to the communication network and adapted to remotely monitor and control an operation state of the protective control apparatuses, wherein each of said protective control apparatuses is provided with means for performing a protective control operation process based on the digital data so as to determine whether or not abnormal data is detected and means for, when the abnormal data is detected as a result of the protective control operation process, transmitting an abnormal data generation information including detection time to the display/operation unit, said abnormal-data being detected at the detection time, and wherein said monitor/control unit is provided with means for transmitting, when the abnormal data generation information including the detection time is transmitted from a predetermined protective control apparatus in the protective control apparatuses, a first program module for collecting digital data before and after the detection time to the protective control apparatuses through the communication network along a predetermined route, said first program module previously being provided in the monitor/control unit; each of said protective control apparatuses being provided with means for receiving the first program module transmitted through the communication network so as to execute the first program module and means for transmitting the digital data having the precise time before and after the detection time to the monitor/control unit in accordance with the first executed program module, said monitor/control unit being provided with means for locating a fault point related to the abnormal data according to the digital data, said digital data having the precise time before and after the detection time and being transmitted from each of the protective control apparatuses.
In preferred embodiment of this still further aspect, each of said protective control apparatuses is provided with: means for reading out predetermined precise time of precise time stored in the storing means of its own protective control apparatus together with the digital data in accordance with a second program module for measuring a power-transmission line constant, said second program module previously being provided in the monitor/control unit and being transmitted through the communication network therefrom, means for measuring the power-line transmission constant by using the digital data of the own protective control apparatus and digital data of at least one of other another protective control apparatuses, said digital data of the own-protective control apparatus being added to the predetermined precise time, means for storing the measured power-transmission line constant and means for calculating a ranging impedance related to an object for the protective control of the own protective control apparatus on the basis of the measured power-transmission line constant.
In preferred embodiment of this still further aspect, said storage means is adapted to store the digital data having the precise time in a period of time from the transmission of the abnormal-data generation information to the monitor/control unit till the transmission of the digital data having the precise time before and after the detection time to the monitor/control unit.
This still further aspect of the present invention has an arrangement that said electric power system and each of said protective control apparatuses are connected to each other through a second communication network which is different from the communication network, said state quantity related to the electric power system being supplied to each of the protective control apparatuses through the second communication network.
In order to achieve such objects, according to still further aspect of the present invention, there is provided a computer-readable storage medium storing a program code for use in a protectively control of a plant, in which the plant has an input device for inputting a state quantity related to the plant therefrom and an opening/closing device for opening and closing a part of the plant, said program code comprising: a first step of causing a computer to acquire precise time; second step of causing a computer to sample the state quantity inputted from the input device according to the acquired precise time so as to convert the state quantity into digital data; a third step of causing a computer to add the precise time at each sampling timing to the digital data so as to transmit the digital data to a communication network, said digital data each having the sampled precise time; a fourth step of causing a computer to perform a control operation according to the digital data transmitted through the communication network; a fifth step of causing a computer to transmit a control command with respect to the opening/closing device through the communication network in response to a result of the control operation of the fourth step; a sixth step of causing a computer to receive, through the communication network, the control command with respect to the opening/closing device; and a seventh step of causing a computer to control an operation of the opening/closing device according to the received control command.
For achieving such objects, according to still further aspect of the present invention, there is provided a method of protectively controlling a plant, in which the plant has an input device for inputting a state quantity related to the plant therefrom and an opening/closing device for opening and closing a part of the plant, said method comprising the steps of: acquiring precise time; sampling the state quantity inputted from the input device according to the acquired precise time so as to convert the state quantity into digital data; adding the precise time at each sampling timing to the digital data so as to transmit the digital data to a communication network, said digital data each having the sampled precise time; performing a control operation according to the digital data transmitted through the communication network; transmitting a control command with respect to the opening/closing device through the communication network in response to a result of the control operation of the performing step; receiving, through the communication network, the control command with respect to the opening/closing device; and controlling an operation of the opening/closing device according to the received control command.
As described above, according to the present invention, the control functions related to the equipment devices (the inputting/outputting devices and the opening/closing device) of the plant, such as the electric power systems, which is protectively controlled are separated from the overall control functions, such as the protective control functions of the overall control system. The separated functions are included by each of the equipment devices so that the control system, such as the electric power system protective control system, is constituted. Therefore, a common hardware configuration realizing the unit included in the same-type equipment devices can be employed, making it possible to reduce the cost of the hardware of the overall control system, such as the electric power system protective control system, and the cost of the software for performing the control operation processes. Thus, the cost efficiency can be improved and the reliability of the software for the control process can be improved.
According to the present invention, the operations of the control apparatuses can accurately be synchronized with each other by using the periodic signals, such as the precise time, making it possible to improve the reliability of the control system. In particular, the control operation process, such as the protective control operation process, can be performed by using digital data on the basis of the state quantity sampled (synchronized) with the same precise time. Therefore, it is able to perform a very accurate control process, such as the process for determining an accident. Thus, a reliable control system can be provided.
According to the present invention, even if a fault takes place in at least a portion of the hardware configuration of the device for inputting/outputting the state quantity and thus an incorrect operation control command are transmitted to the opening/closing device, the fault can be detected thanks to the self-diagnosing means. In accordance with a result of the detection, the locking means inhibits transmission of the incorrect operation control command to the opening/closing device so that the operation control is locked. Therefore, a needless operation control of the opening/closing device caused from a fault of the hardware of the device for inputting/outputting the state quantity can be prevented. As a result, it is possible to improve the reliability of the control systems, such as the electric power system protective control system.
According to the present invention, the control operations, such as the protective control operations, can be performed by using digital data having precise time obtained by adding precise time of the sampling process. Therefore, the control operation processes can be performed by using digital data acquired at distant control stations without any influence of the transmission delay occurring among the control stations (apparatuses). As a result, the reliability of the control system, such as the electric power system protective control system, can be improved.
According to the present invention, digital data having precise time on the basis of the state quantity sampled from a plurality of equipment devices of, for example, the electric power system can time-sequentially be arranged and displayed for each control apparatus in accordance with the added precise time. Therefore, a monitor for monitoring the electric power system, is able to, from each equipment device, accurately and simultaneously (at the same time) compare the sampled state quantities through each control apparatuses. As a result, the reliability of the control system, such as the electric power system protective control system, can be improved.
Moreover, state quantities sampled by each control apparatus can collectively be confirmed from each equipment device of, for example, the electric power system. Therefore, the load and complexity of the operator which is caused from the work for making the rounds the control apparatuses can be overcome. Moreover, the display unit required for each control apparatus can be omitted. Therefore, the cost efficiency can be improved and saving in labor can be realized.
According to the present invention, the state quantity to be tested can be generated in accordance with digital data having the precise time and on the basis of the actual state quantity sampled from a plurality of equipment devices of, for example, the electric power system. The state quantity to be tested can be used in the test of the tested apparatus (the protective control apparatus). Therefore, a test state quantity corresponding to a state quantity corresponding to a complicated system accident which occurs in a complicated electric power system in the form of a superimposed power flow and test state quantity corresponding to change in the power flow of the system during the day of the operation of the system, which have been difficult to be generated for the conventional technique, can significantly easily be generated so as to be used in the test. Therefore, it is possible to improve the reliability and the cost efficiency of the test for confirming the operation of the unit to be tested and the electric power system protective control system.
According to the present invention, each protective control apparatus has a function provided individually from the function of the usual processing unit for determining a fault. The individual function determines whether or not a fault occurs in an equipment device to be protectively controlled in accordance with digital data converted by the converting unit and an equipment device which is not protectively controlled. If a determination is made that a fault occurs, precise time of the sampling operation is added to the sampled digital data so as to be recorded and transmitted to the communication network, making it possible to receive the digital data transmitted through the communication network so as to be arranged. Therefore, it is possible to display the arranged state quantities and to generate the test state quantities by using the arranged state quantities. In addition, the test state quantity can be generated.
The operations for recording, confirming and analyzing of the state quantity acquired by the protective control apparatus which is correctly not operated when an accident occurs in a device to be protectively controlled and an operation confirmation test of the apparatus to be tested can be performed by using the test state quantity corresponding to the state quantity acquired by the protective control apparatus which is correctly not operated, which have been impossible for the conventional technique. Therefore, if a system accident occurs, a total analyzing process and an operation confirmation test using the state quantity of, for example, the overall electric power system obtained from all of the protective control apparatus can be performed regardless of the object to be protectively controlled. Therefore, the reliability of the overall electric power system protective control system can significantly be improved.
According to the present invention, the operation confirmation test of the protective control apparatus to be tested and the protective control apparatus which is correctly operated actually can be performed by using digital data corresponding to the state quantity of each equipment device of, for example, the electric power system without a necessity of using a system simulating unit. Therefore, it is possible to improve the reliability and the cost efficiency of the test for confirming the operation of the electric power system protective control system.
According to the present invention, the power-transmission-line constant can be measured periodically or as necessary by performing the protective control operation process using digital data on the basis of the state quantities sampled at the same time among the plural protective control apparatuses without use of a fixed power-transmission line constant and a measuring unit provided individually from the protective control apparatus. Since the ranging impedance can be calculated by using the measured power-transmission line constant and thus an accident determining process can be performed, the accuracy to detect the accident can be improved and the reliability of the electric power system protective control system can be improved. In addition, the cost of the electric power system protective control system can be reduced.
According to the present invention, one of CPU among a plurality of CPU is caused to perform a data input/output process and a process for analyzing a control demand (the program module) through the communication network. On the other hand, the other CPU is caused to perform the process for collecting digital data and the protective control operation process. Thus, the process for inputting/outputting data through the communication network, the process for analyzing the request for performing control, the process for acquiring digital data in accordance with the state quantity and the protective control operation process can easily simultaneously be performed. Therefore, the efficiency of the protective control operation of the electric power system protective control system can be improved.
According to the present invention, the communication of the state quantity and the operation command signal among the electric power system and the plural protective control apparatuses can be performed by the second communication network provided individually from the communication network for connecting the protective control apparatuses to each other. Therefore, transmission of the state quantity through the communication network for connecting the plural protective control apparatuses is inhibited to considerably reduce the process load which must be borne by the communication network. Since a multiplicity of lines for communicating signals are omitted between the electric power system and the plural protective control apparatuses, the cost of the multiplicity of the dedicated lines and the operation works required to establish the connection of the multiplicity of the dedicated line can be omitted. Therefore, it is possible to reduce the cost of the electric power system protective control system and the amount of the operation for constituting the electric power system protective control system.